package diffblue.flipflop;
   
   import java.util.function.Predicate;
   
   import static java.util.Objects.requireNonNull;
   
   /**
    * Emulates flip-flop logic similar to two-dots flip-flop in Perl or Ruby.
    */
  public final class FlipFlopPredicate<T> implements Predicate<T> {
      private final Predicate<? super T> startPredicate;
      private final Predicate<? super T> endPredicate;
      private boolean state;
  
      public FlipFlopPredicate(Predicate<? super T> lhs, Predicate<? super T> rhs) {
          this.startPredicate = requireNonNull(lhs);
          this.endPredicate = requireNonNull(rhs);
      }
  
      @Override
      public boolean test(final T value) {
          var result = state || startPredicate.test(value);
          state = result && !endPredicate.test(value);
          return result;
      }
  }